About plural: "which is" or "which are"? Ohhhh, I'm not sure, which one is correct: (1) The thing has two parts (X and Y) which is from two different sources: source A and source B. (2) The thing has two parts (X and Y) which are from two diferent souce: source A and source B. sorry, it's a editing error, I wanted to writing as: (1) The thing has two parts (X and Y) which is from two different source: source A and source B. (2) The thing has two parts (X and Y) which are from two diferent souces: source A and source B.